Hello PPRuNers
I have (yet another!) question about professional flying, if you don't mind.
I understand that when you start the take-off roll, you first advance the thrust levers to 70%* N1 to check the engines are spooling up simultaneously and are stable, before then hitting TO/GA (or selecting manually) your take-off thrust (say 90% for sake of argument?).
Sitting down the back, this two-step powering-up of the engines is always noticeable. In fact, I listen out for it. (Incidentally, it can be quite amusing when you occasionally see the look change on people's faces from 'ah, we're off' to 'oh,
now we're off!') But the thing is, it always feel to me that it is the
second increase in power (i.e. selection of T/O thrust) that has the real bite. That's the bit when you get pushed into the back of your seat.
So my question is: why is it that an addition of only 20% gives this effect? Is it because that second increase is more sudden?
As always, I do realise these figures vary from flight to flight. But I hope you understand what I'm driving at. Maybe you have experienced it too?
* 'Facts' based on
this video.